I. Field
The present invention relates generally to electronics, and more specifically to a transmitter/receiver (transceiver) system suitable for a wireless device.
II. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, data, and so on. These wireless systems may be based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), or some other multiple-access techniques. A wireless system may implement one or more standards adopted by a consortium known as 3GPP2, such as IS-2000, IS-856, IS-95, and so on. A wireless system may also implement one or more standards adopted by a consortium known as 3GPP, such as Global System for Mobile Communications (GSM), Wideband-CDMA (W-CDMA), and so on. IS-2000 and W-CDMA are third generation standards for CDMA. IS-95 and GSM are second generation standards for CDMA and TDMA, respectively. These standards are well known in the art.
A wireless communication device (e.g., a cellular phone) utilizes a transceiver system to obtain two-way communication with a wireless system. The transceiver system includes a transmitter for data transmission and a receiver for data reception. On a transmit path, the transmitter modulates a radio frequency (RF) carrier signal with data to be sent to generate an RF modulated signal that is more suitable for transmission. The transmitter further conditions the RF modulated signal to generate an RF uplink signal and then transmits the RF uplink signal via a wireless channel to one or more base stations in the wireless system. On a receive path, the receiver receives one or more RF downlink signals from one or more base stations, and conditions and processes the received signal to obtain data sent by the base station(s).
A wireless system may operate on one or more frequency bands, and a transceiver may have a transmit signal path and a receive signal path for each frequency band used by the wireless system. The transceiver may thus have many signal paths if multiple frequency bands are used by the wireless system. The wireless system may be a time division duplex (TDD) system, such as a GSM system, that transmits and receives in different time intervals. In this case, a transmit/receive (T/R) switch may be used to couple one of the signal paths, at any given moment, to an antenna at the wireless device. The T/R switch has one common RF port for the antenna (which corresponds to a single pole on the switch) and one input/output (I/O) RF port for each signal path (which corresponds to a throw on the switch). For example, a single-pole four-throw (SP4T) T/R switch may be used in a dual-band GSM transceiver having two transmit paths and two receive paths. As the number of signal paths increases to support more frequency bands, more I/O RF ports are needed for the T/R switch. The design of the T/R switch becomes more complex and performance degrades as the number of I/O RF ports increases.
A multi-mode wireless device (e.g., a dual-mode cellular phone) may be capable of communicating with multiple wireless systems (e.g., GSM and CDMA systems). This capability allows the multi-mode device to receive communication services from more systems and enjoy greater coverage provided by these systems. A multi-mode transceiver may have many signal paths to support all of the frequency bands used by all of the wireless systems. Interconnecting all of these signal paths to the antenna may require a complicated T/R switch with many I/O RF ports.
There is therefore a need in the art for a transceiver system capable of supporting multiple frequency bands for multiple wireless systems and having reduced complexity.